Mechanical Properties Of Magnetorheological Fluids Research Articles

An experimental study on mechanical properties of a magnetorheological fluid under slow compression

Mechanical properties of magnetorheological (MR) fluids have been investigated in slow compression under different magnetic fields. The compressive stress of the MR fluid has been deduced by assuming that it was a continuous shear flow in Bingham model and has been calculated. The compressive stress has also measured in different magnetic fields and initial gap distances. The compressive stress of the MR fluid in a high magnetic flux density and/or a small initial gap distance was much higher than that predicted by the traditional continuous media theory. Compressive experimental results were also compared with the continuous media theory by a normalized logarithmic form. The achieved experimental result seems to deviate from the prediction by the continuous media theory at a high magnetic flux density and a small initial gap distance. The MR fluid had a high compressive modulus when the compressive strain was lower than 0.042. The compressive modulus had an exponential relationship with the compressive strain higher than 0.042. Frictions between particles, which contribute to the high structure factor, were thought to play an important role in the large deviations in squeeze mode.

STUDY OF FACTORS INFLUENCING THE WALL SLIP OF A MAGNETORHEOLOGICAL FLUID

The wall slip of magnetorheological (MR) fluids refers to a phenomenon that affects the application of mechanical properties of magnetorheological fluids due to the relative slippage between the magnetic particles and the transmission wall. In this paper, we analyze and experimentally verify the factors affecting the wall slip of magnetorheological fluids, which can limit the application of magnetorheological-fluid devices. Firstly, from the theoretical point of view, it is considered that the influencing factors are mainly divided into two parts: magnetorheological fluid’s own parameters and transmission surface roughness, among which the parameters include viscosity, mass fraction, etc. When studying the influence of the transmission surface roughness, it is found that different surface morphologies have a great influence on the shear stress. Secondly, a magnetic field simulation analysis and shear yield stress experiments are conducted on shear blocks with different surface morphologies; the obtained results are compared and verified, confirming that different surface shapes affect the shear yield stress by changing the magnetic field distribution of the groove, which in turn changes the wall slip characteristics. These findings provide an effective basis for further research on the wall slip of magnetorheological fluids to improve the transmission effect.

Macro-mechanical properties of magnetorheological fluids based on body-centered cubic structure

This paper addresses the problem that the microstructure model of magnetorheological fluid established by traditional single-chain or multi-chain dense rows is unable to accurately describe the rheological behavior and the sudden change of macroscopic mechanical properties under the action of an applied magnetic field, and analyzes the stable cluster-like structure formed by a specific volume fraction of magnetorheological fluids in a micro-narrow channel under the action of external magnetic field and extrusion pressure. This paper also establishes the equations of motion and dynamics of magnetic particles under the action of external magnetic field, analyzes the dynamic evolution of particle microstructure, performs numerical simulations of two-dimensional chaining using Matlab, and establishes a microscopic observation test bench for comparison and verification; and it establishes a model of complex cluster-like structure of magnetorheological fluids body-centered cubic, and analyzes the system energy, stability and force of the body-centered cubic structure based on the minimum system energy theory and Hertzian contact theory; and further establishes a shear yield stress model based on the body-centered cubic microstructure to analyze the macroscopic mechanical properties of magnetorheological fluids, thereby enriching the theoretical system of extrusion strengthening of magnetorheological fluids in the microscale.

A Novel Dual Helical Magnetorheological Fluid Micro-Robot

To address the problem of flexible drive control of gastrointestinal (GI) tract micro-capsule robot posture, a novel dual helix magnetorheological fluid (MRF) micro-robot (DHMRFMR) is proposed and developed in this paper. Based on the mechanical properties of magnetorheological fluid, the relationship model of magnetic field force is obtained, and the thrust model is established. Double micro DC deceleration motor is used to drive the two ends of the helical actuator to make the DHMRFMR forward and backward, by changing the external magnetic field rotation speed, direction and distance, adjust the attitude direction of the robot. Numerical simulation software ANSYS is used to analyze the motion law of external fluid of DHMRFMR, and the visualization of fluid velocity and pressure distribution is realized. The front-end helix actuator can change the flow path of the fluid, and the middle and tail of the DHMRFMR bear less pressure, which improves the stability and flexibility of the robot. The novel DHMRFMR is suitable for internal drive in bending environment, and has a good application prospect in biomedical engineering field in human intestinal unstructured environment.

Study on the Influence of Temperature–Magnetic Field Coupling on the Mechanical Properties of Magnetorheological Fluids

The composition of a magnetorheological fluid (MRF) usually includes magnetic particles, a carrier fluid, and additives. Among them, the magnetic particles and carrier fluid are the main sources of the mechanical properties of the MRF. The changes of the related properties of the two will affect the mechanical properties of the MRF directly or indirectly. Herein, first, the temperature–magnetic field characteristics are analyzed during the MRF working process. Then, the influence mechanism of temperature and magnetic field changes on the properties of the magnetic particles and carrier liquid are analyzed. On this basis, the traditional Bingham model is improved and optimized, in which the temperature variable is introduced to represent the effect of temperature–magnetic field coupling on the shear stress of the MRF. Finally, parameter fitting and simulation are carried out for the optimized model, and the self‐made shear stress of the MRF measuring device with temperature‐control function is used to experimentally verify the accuracy of the optimized model. The comparison and verification of the results show that the optimized model can better represent the variation of shear stress of an MRF with temperature and magnetic field than the traditional Bingham model.

A systematic study of the impact of additives on structural and mechanical properties of Magnetorheological fluids

Magneto rheological fluids, often called smart fluids, play a significant role in effective mechanical braking systems, haptic devices, mechanical dampers and other mechanical devices. Presently, the properties of Magneto rheological fluids added with additives or nanoparticles were discussed. The introduction of an additive/nanoparticle in MR fluid alters the mechanical, thermal, structural and other properties of the fluid. The characteristic feature of this fluid is that they become solidified under the effect of an applied magnetic field. This is mainly due to the chain development of suspended molecules in the fluid medium. When these fluids are mixed with nanoparticle additives, these chain forms become stronger, as the nanoparticles occupy the spaces among the molecules of MR fluid. This in turn increases the dispersion stability, yielding strength of the fluid under action. Due to higher solubility of suspended iron particles, the Carbonyl Iron based MR fluid is the most commonly used MR fluid.

Experimental study on tensile mechanical properties of magnetorheological fluid

Magnetorheological fluid (MRF) is a kind of suspension composed of a nonconducting magnetic liquid and small soft magnetic particles with high permeability and low hysteresis. The tensile mechanical properties of MRF reflect its important mechanical properties. In this study, a testing device is designed to investigate the tensile mechanical properties of MRF in accordance with the plate method theory. First, the magnetic field is selected to analyze the influence of different gap sizes on the magnetic field. The magnetic field strength decreases as the gap increases. Second, a testing platform for tensile mechanical properties is built, and the tensile mechanical properties of MRF are experimentally studied under different magnetic field strengths, tensile speeds and surface characteristics. Experimental results show that the stronger the magnetic field, the greater the tensile yield stress. The maximum tensile stress at different velocities is nearly the same. Different surface characteristics affect tensile stress.

Measurement of temperature-dependent mechanical properties of magnetorheological fluids using a parallel disk shear stress testing device

Mechanical properties are critical to the working performance of magnetorheological fluids (MRFs), especially in high temperature situations. This paper presents an experimental investigation to analyze the effects of temperature on mechanical properties of MRFs. First, a parallel disk method was implemented for the shear stress measurement of MRFs and the measurement principle was theoretically illustrated. Then, a detailed introduction to the MRF sample preparation and the testing device development was performed as well. In the study, five kinds of MRF samples with different material parameters were prepared and a shear stress testing device which possesses the temperature control function was developed and evaluated. After these, a series of measurements were conducted on the viscosity–temperature characteristic, shear stress–temperature characteristic and thermal stability of MRF samples. Measuring results indicated that the mechanical properties of MRFs were obviously dependent on temperature. The phenomenon mainly embodied in the reduction of off-field viscosity and shear stress with increasing temperature, as well as the performance degradation after undergoing a low–high–low temperature cycle or a high temperature treatment of more than 150 ℃.

Testing device and experimental investigation to influencing factors of Magnetorheological fluid

More attentions have been paid to Magnetorheological fluid, which is a kind of new functional materials. An elegant device is designed for the test of the mechanical properties of Magnetorheological fluid, and the mechanical properties of ten samples of Magnetorheological fluid are tested with the device. In the experimental investigation, we choose ten samples of Magnetorheological fluid to analyze and obtain the material parameters with the testing device. The effects of the typical influencing factors, such as magnetic induction intensity, ferromagnetic particle volume fraction, base solutions, temperature, shear strain rate, response time, sedimentation stability, yield shear stress, viscosity and zero-field viscosity, etc, are investigated. This work proves that Magnetorheological fluid is reliable and practical through experimental results. We welcome warmly the relevant experts and scholars to exchange and guide further.

Influence of Different Gradation Carbonyl Iron Particles on the Properties of Magneto-Rheological Fluids

The influence of carbonyl iron particles sizes on the properties of magneto-rheological fluids (MRFs) were studied. Different-sized carbonyl iron magnetic particles were prepared by ball milling with different milling times. On this basis, different particle MRF were prepared The off-state viscosity and the shear stress of the above MRFs were characterised and studied by an advanced rotational rheometer system. The test results show that the off-state viscosity and the shear stress of single-particle MRFs were enhanced with increasing average carbonyl iron particle size at a constant magnetic field. The shear stresses of MRFs containing two or three different particle sizes were significantly improved compared with the MRFs containing only a single particle size. At a reasonable level of medium and small size carbonyl iron particle spread throughout the structure of the multiple-particle MRFs, the defects in the chain structure were remedied when a chain reaction occurred, and the mechanical properties of MRFs were enhanced. Meanwhile, increased mass fractions of the small size carbonyl iron particle resulted in a reduction in overall average particle size of MRFs, and the mechanical properties of MRFs were also reduced. The mechanical properties of multiple-particle MRFs were observed to be strongly dependent on the size and mass fraction of the medium and small carbonyl iron particles.

Influence of Different Gradation Carbonyl Iron Particles on the Properties of Magneto-Rheological Fluids

The influence of carbonyl iron particles sizes on the properties of magneto-rheological fluids (MRFs) were studied. Different-sized carbonyl iron magnetic particles were prepared by ball milling with different milling times. On this basis, different particle MRF were prepared The off-state viscosity and the shear stress of the above MRFs were characterised and studied by an advanced rotational rheometer system. The test results show that the off-state viscosity and the shear stress of single-particle MRFs were enhanced with increasing average carbonyl iron particle size at a constant magnetic field. The shear stresses of MRFs containing two or three different particle sizes were significantly improved compared with the MRFs containing only a single particle size. At a reasonable level of medium and small size carbonyl iron particle spread throughout the structure of the multiple-particle MRFs, the defects in the chain structure were remedied when a chain reaction occurred, and the mechanical properties of MRFs were enhanced. Meanwhile, increased mass fractions of the small size carbonyl iron particle resulted in a reduction in overall average particle size of MRFs, and the mechanical properties of MRFs were also reduced. The mechanical properties of multiple-particle MRFs were observed to be strongly dependent on the size and mass fraction of the medium and small carbonyl iron particles.

A Micromechanical Model for Magnetorheological Fluids

The rheological and mechanical performances of a magnetorheological (MR) fluid depend on the induced solid microstructure under an applied field. In this study, the interaction between particles is analyzed, based on the microstructure with the applied field, and a micromechanical model is proposed to describe the constitutive behavior of MR fluids by making use of static magnetics. It can take into account the effects of the intensity of the applied magnetic field, the particle size and particle volume fraction, the magnetic property of the particle, and the viscosity of the carrier fluid, on the mechanical properties of MR fluids. The yield shear stress is analyzed and calculated based on the theory of magnetics and statistical analysis. The satisfactory agreement between the analytical and the experimental results demonstrates the validity of the proposed model in describing and optimizing the properties of MR fluids.